The present invention relates to a method and apparatus used to lay railroad track and more particularly to such a method and apparatus used to lay the track on concrete supports.
The field of laying tracks for railroads is one of the oldest and most highly developed of the industrial arts. The most widely used method of railroad track laying, and one which is still practiced, involves forming a railroad right-of-way, for example, an earthenwork embankment, upon which is laid a top layer of gravel or stones. A series of parallel chemically impregnated wooden railroad ties are laid on the gravel and perpendicular to the direction of the steel rails. The ties are partially buried in additional gravel or stones. The rails are lowered into the ties and held in place by railroad spikes which are driven into the wooden ties. The spike's head has an elongated portion which overlaps the bottom flange of the railroad track.
In recent years there has been increased emphasis on the use of concrete railroad ties. Such ties are particularly useful in areas in which there is little or no wood and are generally considered to be superior to wooden ties for use on heavily travelled routes and high-speed tracks.
One type of system used to removably fasten the railroad track to a concrete tie is known as the "Sidewinder" system, a trademark of Portec Inc., Oak Brook, Illinois. In that system a "shoulder-pin" fixation member has an elongated pin (rod) portion with indentations and is adapted to be held in the concrete. A shoulder portion sits on top of the concrete tie and has a three-point suspension system. A strong metal clip, which is a unitary member acting as a series of torsion and bending springs, fits in a hole through the shoulder and an indentation in the shoulder, with one of its arms acting against the flange of the railroad track. An external insulated plate may be used between the clip and the tie and a resilient rubber pad may be used between the bottom of the steel railroad track and the top of the concrete tie.
In addition, it has been suggested that, instead of using individual ties, larger pre-cast concrete slabs may be used to support the rails. It has also been suggested that such concrete slabs may be insulated from the road bed by resilient rubber isolation pads to provide damping of noise and vibration.